1. Field of the Invention
The present invention relates to a method for producing a positive charging toner.
2. Description of the Related Art
In an electrophotographic or an electrostatic recording image forming apparatus, an image can be formed on a piece of paper by supplying a toner that is charged with a predetermined polarity and to a predetermined amount of charge, to an image forming section thereby distributing the toner over the paper so as to form the image, through the effect of an electric field, and then fixing the toner thus distributed over the paper.
The toner may be a magnetic two-component toner, in which the toner is charged through frictional charging by a magnetic carrier, or a non-magnetic mono-component toner, which is charged by friction with a contact section of the image forming apparatus, without using any magnetic carrier. Non-magnetic mono-component toners are advantageous for reducing the size of the image forming apparatus.
In order to stably obtain fine images in the above recording methods, it is important to stabilize the charge characteristics of the toner; namely, to make the charge distribution as uniform as possible while ensuring a sufficient charge amount. In order to stabilize the charge characteristics of the toner, control of the toner charge characteristics by means of a charge control agent is particularly important in the non-magnetic mono-component toners.
Conventional production methods of such toners include methods that involve synthesizing base particles by emulsifying a binder resin in a liquid. In such base particle synthesis methods, a suspension of static control microparticles comprising polar groups is supplied to a suspension of base particles comprising a negatively chargeable binder resin such as polyester, to stably fix the electrostatic control microparticles onto the surface of the base particles (as disclosed in Japanese Patent Application Laid-open No. 2007-94041). There have also been disclosed methods for washing toner base particles comprising a static control agent, to thereby keep conductivity at or below a predetermined value with a view to curbing variation in the charge amount of the toner base particles (Japanese Patent Application Laid-open No. 2000-292976).